The invention concerns an analytical balance with a four-bar mechanism which keeps the balance pan parallel horizontally during its vertical travel, the one vertical side of which is held fast to the housing, the other vertical side of which in the form of a coupling piece carries an extension which receives the scale, and both horizontal sides of which are connected in an articulated manner by an upper and a lower rod to the vertical sides, whereby the four-bar mechanism is loaded by the restoring force of a load converter. Such analytical balances are known in the literature, e.g.:
Swiss patent No. 397,262 PA2 United Kingdom No. 7,112,179; PA2 DE-OS No. 3,114,103; PA2 DE-GM No. 82 03 807.4; PA2 DE-GM No. 82 03 094.4.
One or more regulating weights are positioned directly under the scale for regulating the balance. These regulating weights can be coupled by a raising mechanism for the regulating process in a loading manner to the scale carrier and are disengaged, thus removing the load, for normal weighing operations. It is also known that so-called substitution weights can be positioned directly under the pan on the pan carrier in order to extend the weighing range in a substituting manner by disengaging corresponding individual substitution weights from the pan carrier as the load increases.
The positioning of an extension or bracket for receiving the pan has certain constructional, formational and operational advantages compared with the positioning of the load scale directly in the axis of the load receiver or coupling piece in the four-bar mechanism. There is, however, the danger in the selection of such a contruction principal that damaging torques can be initiated in the sensitive bending springs via the deformation of the coupling piece due to the bracket and the behaviour of the balance in the case of off-center loads on the scale becomes unfavorable, that is, the so-called corner load behaviour becomes worse.
In a known analytical balance of the type initially mentioned the extension is mounted over the lower rod plane to the coupling piece, while the bearing consists of two short brackets projecting on both sides on the coupling piece toward the actual extension. The actual extension is supported on both sides on these brackets. The extension consists of two bars which enclose the cross-section of the coupling piece and are supported on the short brackets by means of two cross-pieces. The extension is mounted on the coupling piece so that it can pivot in a limited horizontal manner in order to take up any lateral jolts acting on the scale. These bearings offer additional moments of danger and increase the sensitivity of the construction to corner loads acting on the pan.